Copy the state of the given object onto the persistent object with the same identifier. If there is no persistent instance currently associated with the session, it will be loaded. Return the persistent instance. If the given instance is unsaved, save a copy of and return it as a newly persistent instance. The given instance does not become associated with the session. This operation cascades to associated instances if the association is mapped with cascade=”merge”.
In short, inserting and fetching BLOB data such as images requires two steps: define database column type as “BLOB” and have a field in entity of type “byte array”.